DESCRIPTION (Adapted from Applicant's Description: In the presence of spastic paresis due to incomplete spinal cord injury (SCI), inadequate supraspinal contributions to motor output of the lower extremities result in a number of abnormalities of movement. Among these are unregulated spinal reflexes, inadequate and delayed motor recruitment, and balance deficits. If the individual is ambulatory, these abnormalities are manifest in the resulting gait pattern as aberrant temporal relationships between muscle groups, deficits in weight bearing capacity and inappropriate muscle activity such as prolonged stance phase, clonus and "scissoring." Sensory information from multiple sources contributes to the production of vertebrate locomotion, therefore, by manipulating sensory input it is possible to modify motor output. Two innovative technologies that appear to be effective for achieving this end are body weight support (BWS) and functional electrical stimulation (FES). The capacity of the human spinal cord to respond to and benefit from an innovative treadmill training regimen will be assessed. FES will be used in conjunction with BWS to facilitate locomotor performance on a treadmill in individuals with incomplete SCI. Preliminary studies indicate that, by combining these interventions, gait performance is improved such that more efficient and functional movement is allowed to emerge. The influence of the body weight support and of appropriately timed stimulation on the resulting ipsilateral and contralateral motor outputs will be characterized. The training effects of BWS locomotion augmented by FES over the course of a multi-session training program will be examined. Gait parameters modified by training will be identified and the nature of these changes will be characterized. To further study how BWS may affect spinal neural elements, a second set of experiments will investigate the effects on alpha motoneuron excitability of unloading the lower extremities, in individuals with incomplete SCI and able-bodied (AB) controls. The proposed experiments are to test the hypothesis that (1) locomotor capacity in individuals with incomplete SCI can be positively influenced by a training regimen consisting of BWS in conjunction with FES, and (2) unloading of the lower extremities influences motoneuron excitability in humans. Results from this work are envisioned to provide the foundation on which to develop rehabilitation protocols for SCI individuals with residual locomotor capacity.